ELISA - exam 2

What was this lab testing for?

disease antigen in plant fluid

What does a blue well mean?

antigen present, positive result

What does no color mean?

no antigen detected, negative result

What is an antigen?

the pathogen molecule being detected

What first sticks to the plastic well?

proteins from the sample

What does the primary antibody bind to?

the disease antigen

What does the secondary antibody bind to?

the primary antibody

What is attached to the secondary antibody?

an enzyme

What does the enzyme substrate do?

turns blue if the enzyme is present

What is the full ELISA chain?

Antigen → primary antibody → secondary antibody → enzyme → blue color

Why wash the wells?

to remove unbound material

What can happen if you do not wash the wells after every step?

false positive

Why use fresh tips?

prevent contamination

What is a positive control?

a known antigen sample that should turn blue

What is a negative control?

a known no-antigen sample that should stay colorless

Why use controls?

to prove the test worked

What can cause a false negative?

low pathogen, wrong tissue, early infection, dilution, lab error

Why assay samples in triplicate?

to make results more reliable and catch errors

If you tested positive for pathogen exposure, did you have direct contact with one of the original infected plants?

tested positive, but didn’t directly contact infected plants

=

disease spread indirectly through other student’s shared samples

If you didn’t test positive, what conclusions can you reach about transmissibility of disease in a population?

disease can spread indirectly through a chain of contacts, not only from the original infected source

ELISA core process

antigen sticks to well → primary antibody binds antigen → secondary antibody binds primary antibody → enzyme substrate turns blue

Blue =

antigen present

Antigen present =

positive

No color =

no antigen detected

No antigen detected =

negative